Mercury switch



March 14, 1939. H. A. DUDGEON MERCURY SWITCH Filed Oct 15, 1936 5 Sheets-Sheet 1 swam bob FIG "HARR Y A. .DLJDG'EUN March 14, 1939. H. A. DUDGEON MER URY SWITCH Filed Oct. 15, 1936 5 Sheets-Sheet 2 E Ill lp|fialurll MUN H llll 3 I F II|IL WHIIIIII|M.IIII| I P I uln l llllrlll lrt HARRY Pad 2 1 .DLJDGEUN L L l March 14, 1939. A, DUDGEON 2,150,674

MERCURY SWITCH Filed Oct. 15, 1936 3 Sheets-Sheet 3 Ema/Maw H R Y A. .DUDGEUN Patented Mar. 14, 1939 UNITED STATES PATENT OFFICE MERCURY swrron Application October 15, 1936, Serial No. 105,739 In Great Britain November 16, 1935 8 Claims. (Cl. 20052) The invention relates to mercury switches especially in connection with sizing apparatus and, with regard to its more specific features, for use in connection with grinding machines.

One object of the invention is to provide a work sizing apparatus and mercury switch therefor with a temperature compensator. Another object of the invention is to provide a temperature compensator of the type above indicated which is automatic in its operation. Another object of the invention is to provide a sizing device and mercury switch incorporated in a unit and pro vided with facile means for adjustment to fulfil the requirements of hard practical use. Another object of the invention is to provide a mercury switch sizing device of rugged construction incorporated in an integral unit. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangement of parts, all as will be exemplifled in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings which, taken as a whole disclose the mechanical features of this invention in its several aspects,

Figure 1 is a view partly in elevation and partly in section more particularly illustrating certain features of construction;

Figure 2 is a vertical sectional view taken on the line 2--2 of Figure 1 looking in the direction of the arrows;

Figure 3 is a broken sectional view taken on the line 3-3 of Figure 1 looking in the direction of the arrows;

Figure 4 is an elevation of the apparatus which incorporates the non-automatic temperature compensator;

Figure 5 is a vertical sectional view taken on the line 55 of Figure 4 looking in the direction of the arrows;

Figure 6 is a plan view of the apparatus of Figure 4;

Figure '7 is an elevation of the apparatus which incorporates the automatic temperature compensator.

In the several views similar parts are denoted by the same or similar symbols.

Referring to Figures 1, 2, and 3, the switch consists of a body A which is capable of being moved towards and away from the work D4 be ing ground, in the V slide B. Any known means may be employed for moving the body, for example by a screw and nut, and the slide is mounted on the machine table of a grinding machine or any other suitable support. Drilled at an angle in the body is a hole Al which connects a recess A2 with the tube 0', the recess and tube containing mercury to the level E. The front of the recess is closed by a diaphragm D which is sccured to the body by a ring DI and screws D2, a jointing material such as rubber, paint, or the like, being inserted between the face of the body and the diaphragm to prevent mercury from escaping. Attached to the diaphragm is a contact point D3 which touches the surface of the work. The tube C, which may be of glass or other transparent material, is secured in position in the body by a nut Cl and rubber bush C2. The height of the mercury in the tube is adjusted by a screw El, the screw being locked by a nut E2.

Secured to the body is a spindle F which carries a sliding head G, the head being electrically insulated from the spindle by vulcanite bushes Fl, F2. A spring F3 presses the head upwards, the movement being controlled by a nut F4. A pointer F5, secured to the head by a screw F6, is provided so that the head may be adjusted rela-= tive to the upper surface E of the mercury.

Carried by the head is an adjustable screw GI which has connected to its lower end an extension G2 and which is the end of an electric circuit, the screw GI being locked by a screw G3. A wire G6 attached to the head by a screw G5 forms a continuation of the electric circuit. Carried by the screw GI is a non-metallic screw H in which is inserted a metal pin HI and which forms the end of another electric circuit, connection being made between the upper end of the pin and a wire H2, which forms the continuation of the electric circuit, by a fiat spring H3. The spring and the wire are electrically insulated from the head by mica strips H4, the wire, spring, and strips being secured to the head by screws H5.

The action of the device is as now described:

When pressure is applied to the contact point D3 by the surface of the work D4, mercury in the recess A2 is forced up the tube C and makes contact with one or both of the terminals G2, HI, thereby closing one or two electric circuits, electric currents flowing through the wires G6, H2 through the desired electric mechanism, such as an electric motor controlling the in-feed of the grinding machine, operating a solenoid, lighting a lamp or the like, and back through a wire A4, which is secured to the body by a screw A5, and through the body A and mercury to complete the circuit. As pressure on the ill diaphragm decreases, through the diameter of the work being reduced, mercury in the tube C will fall and when it falls below the end of the terminal G2 the current will be interrupted, thereby stopping the action that current was performing, or initiating an action by deenergizing a spring opposed solenoid. Likewise further decreased pressure on the diaphragm will cause mercury in the tube to fall below the end of the terminal HI thereby interrupting the current passing through HI and its connections, and stopping the action that current was performing or initiating another action by deenergizing a spring opposed solenoid. The head is adjustable to enable the terminals G2, Hi to be simultaneously adjusted relative to the surface E of the mercury. The screws GI, H are adjustable relative to each other and to the head, thus permitting independent fine adjustment of the terminals relative to the mercury.

Figures 4, 5, and 6 illustrate features involving the provision of an additional mercury recess J and a glass tube K, no passage for mercury being provided between the two recesses A2 and J, but there being a hole A3 which connects the recess J with the tube K. The front of the recess J is closed by a diaphragm L, ring Li and screws L2, a jointing material being provided between the body and the diaphragm as previously described. No contact point is provided on the diaphragm L as it is not subjected to pressure. The tube K is secured in position in the body by a nut M and a rubber bush in a similar manner to that described for the tube C. Mercury partly fills the tube K and entirely fills the recess J. The height of the mercury in K is adjusted by the screw 0, and which is locked by the nut OI. A line NI is marked on the head G so that the head may be adjusted relative to the surface of the mercury.

The volume of mercury in the recess J and tube K bear the same ratio to the mercury in the recess A2 and tube C as the cross sectional area of the tube K bears to the cross sectional area of the tube C, and which ensures that the rise and fall of the mercury in the two tubes due to temperature variations will synchronize. The purpose of the recess J and tube K is so that adjustments of the head G may be made, by hand, to compensate for temperature variations of the mercury, and independently of the height of the mercury in the tube C, the height of which may vary through either pressure on the diaphragm D, or temperature of the mercury, or both.

Figure '7 illustrates further features in which means are provided for automatically maintaining the predetermined relative relationship between the ends of the terminals G2, HI and the surface of the mercury E, independently of temperature variations of the mercury. In this construction the head G is mounted on the end of a piston P which has a sliding fit in a guide Pl, the piston being in contact with and supported by the mercury in the recess J. The volume of mercury in the two sides of the device will be proportional to the cross sectional areas of the piston and tube C so that the vertical movement of the piston will synchronize with the movement of the mercury in the tube. The head may be adjusted vertically by a screw Q and locked by a nut QI. Means are provided for filling the recess J with mercury so as to exclude air from between the mercury and the end of the piston, for example by a cup R formed on the body A and hole RI, the piston being raised until its lower end is level with the upper edge of the hole RI when mercury is poured into the cup. After filling the recess a screw R2 closes the hole RI and the screw Q is adjusted to bring the head G into the desired position.

When any of the forms of construction described are used to indicate relative movement between two parts the body is attached to one of the parts with the contact point D3 bearing against the other part. The device is adjusted until pressure on the diaphragm causes mercury to rise in the tube and close an electric circuit. If movement takes place between the two parts so that pressure on the diaphragm is reduced, the mercury in the tube will fall and break the electric circuit. Likewise if there is a space between the contact point D3 and the other of the two parts, movement of the two parts together when pressure is applied to the diaphragm closes one or more electric circuits.

Any of the devices described may be arranged to indicate variations in diameter or thickness or articles being measured, for example the devices may be mounted in such manner that the contact point D3 is normal to a plane surface, and

the distance between the point and the siulace adjusted so that when an article of given size is placed between them the mercury in the tube makes contact with the lower of the two terminals and a lamp of a given color lights up.

If the articles are so large that, on this account, increased pressure on the diaphragm causes the mercury to make contact with the upper of the two terminals, a lamp of another color is caused to light up and thus the device becomes a limit gauge or indicator.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinbefore set forth together with many thoroughly practical advantages are L cluding a flexible diaphragm which form a fluid F reservoir, a conducting fluid therein, an electric circuit including said fluid and a terminal located above but engageable by the fluid, means for moving the diaphragm and causing relative movement of the fluid and terminal and means governed by a temperature volume change of said fluid whereby the fluid and terminal may be moved relatively to compensate for said change.

2. An electrical control device comprising walls including a flexible diaphragm which form a fluid reservoir, a conducting fluid therein, an electric circuit including said fluid and a terminal located above but engageable by said fluid, means for moving the diaphragm and causing relative movement of the fluid and terminal, means for ascertaining the volume change of said fluid under temperature changes and means for moving the fluid and terminal relatively to compensate for such volume change.

3. An electrical device comprising walls inl for moving the diaphragm and causing relative (iii movement of the fluid and terminal, a second reservoir of said fluid and means governed by temperature volume changes of the fluid in the second reservoir whereby said terminal and the associated fluid may be moved relatively to compensate for temperature volume changes.

4. An electrical device comprising walls including a flexible diaphragm forming a fluid reservoir, a switch chamber communicating therewith which has a small cross section compared with the area of the diaphragm so that, a slight movement of the diaphragm will cause a considerable movement of fluid therein, fluid within said chambers with its normal level below the upper end of the switch chamber, an electric circuit comprising said fluid and a terminal in the switch chamber engageable by the fluid, a second reservoir of said fluid and means governed by temperature volume changes of the fluid in the second reservoir whereby said terminal and its fluid may be moved relatively to compensate for the temperature volume changes.

5. An electrical device comprising walls including a flexible diaphragm forming a fluid reservoir, a conducting fluid therein, an electric circuit including said fluid and a terminal located above but engageable by said fluid, means for moving the diaphragm and causing relative movement of the fluid and terminal, and means actuated automatically by the expansion of said fluid which causes a relative movement between the fluid and terminal and compensates for a temperature volume change of the fluid in said reservoir.

6. An electrical device comprising walls including a flexible diaphragm forming a fluid reservoir, a conducting fluid therein, an electric circuit including said fluid and a terminal engageable thereby, means for actuating the diaphragm and moving the fluid relative to the terminal, a second reservoir of the fluid and means operated by a temperature volume change of the fluid in the second reservoir which automatically moves the terminal and its associated fluid relatively and compensates for a temperature volume change of the fluid.

'7. An electrical device comprising walls including a flexible diaphragm forming a fluid reservoir, a conducting fluid therein, an electric circuit including said fluid and a terminal engageable thereby, means for actuating the diaphragm and causing relative movement of the fluid and terminal, a second reservoir containing the same fluid therein, means indicating the level of the fluid in the second reservoir and manually operated means for moving the terminals and fluid relative to each other in the first reservoir as governed by the height of the fluid in the second reservoir and thereby compensating for a temperature change.

8. An electrical device comprising walls including a flexible diaphragm forming a fluid reservoir, a conducting fluid therein, an electric circuit including said fluid and a terminal engageable thereby, means for actuating! the diaphragm and causing relative movement of the fluid and terminal, a second reservoir containing the same fluid therein, a piston moved by expansion of the fluid in the second reservoir and means connecting said terminal with the piston whereby the position of the terminal will be governed by temperature volume changes in the second reservoir. I

HARRY ALLSOP DUDGEON. 

